There's one fundamental difference between the new White House and the old when it comes to immigration: Barack Obama ordered his administration not to enforce a number of immigration laws. Donald Trump has ordered his administration to enforce them.

Trump's two immigration executive orders, issued last Wednesday, are long, far-reaching, and complicated. But perhaps the most consequential passage in the two combined orders is a single sentence: "The purpose of this order is to direct executive departments and agencies to employ all lawful means to enforce the immigration laws of the United States."

That is the heart of Trump's immigration strategy. "We do not need new laws," the president said at the Department of Homeland Security Wednesday. "We will work within the existing system and framework."

Trump's proposal to build a wall on the Mexican border dominated coverage of the two executive orders. But the orders do much, much more than that -- or at least they start the process of doing much, much more. For those who follow immigration closely, the Trump orders contain several critical provisions. Among them:

1) End "catch and release." In the Obama years, as thousands of people, mostly from Central America, crossed the Mexican border illegally -- and made no effort to escape apprehension, asking for a "permiso" to stay -- the border authorities would briefly detain them, give them a date to show up in court, and let them go. The practice was known as "catch and release."

It did not take a rocket scientist to predict that most, now safely inside the U.S., would not show up for court. With family units who arrived in that fashion, immigration court statistics gathered by the Center for Immigration Studies (a group which favors tighter immigration restrictions), reveal that 84 percent do not show up in court.

Under Trump's new directive, the Department of Homeland Security will now detain those illegal crossers and handle their cases on the spot. "The Secretary (of DHS) shall immediately take all appropriate actions to ensure the detention of aliens apprehended for violations of immigration law," the order on border enforcement says, "pending the outcome of their removal proceedings or their removal from the country to the extent permitted by law."

2) Put pressure on "sanctuary cities."

"Sanctuary jurisdictions across the United States willfully violate Federal law in an attempt to shield aliens from removal from the United States," the Trump order on interior enforcement says. The order would give the Attorney General and Secretary of Homeland Security the authority to determine "that jurisdictions that willfully refuse to comply with (federal law) are not eligible to receive federal grants, except as deemed necessary for law enforcement purposes by the Attorney General or the (DHS) Secretary."

Some leaders of sanctuary cities are already promising to fight the federal government. But some will likely yield to federal pressure -- a remarkable change from the Obama years.

3) Speed deportations. Both the Obama administration and now Trump said they want to remove illegal immigrants who have committed serious crimes. But Obama waited until the immigrant in question had been convicted before even beginning what could be a lengthy removal process. The Trump interior enforcement order allows removal paperwork to begin at the time an illegal immigrant is charged, on the reasonable assumption that a person who is in the United States illegally to begin with, and is then charged with at least one additional crime, does not have a right to stay in the country indefinitely.

4) Follow the law in deporting "removable" illegal immigrants. "We cannot faithfully execute the immigration laws of the United States if we exempt classes or categories of removable aliens from potential enforcement," the order on interior enforcement says, referring to illegal immigrants who have been convicted of crimes, and in some cases deported multiple times, only to return to commit more crimes and endanger local communities. "I hereby direct agencies to employ all lawful means to ensure the faithful execution of the immigration laws of the United States against all removable aliens."

5) Stop automatically allowing asylum seekers to stay while their cases are considered. Thousands of people come to U.S. ports of entry along the Mexican border from places like Haiti, India, China, and elsewhere -- all claiming asylum. The Obama administration allowed them to stay in the country while their cases were adjudicated. Many simply skipped out on the process and stayed permanently.

The new executive order would require those asylum seekers to apply for asylum and then wait for a decision not in the U.S., but in Mexico or Canada. Then, if they are allowed in, they're in. But if asylum is not granted, they won't have been permitted to disappear into the United States.

6) Inform the public. In the Obama years it was sometimes hard to find good statistics about illegal immigrants who were accused of crimes. Trump seeks to change that. From the interior enforcement order: "To promote the transparency and situational awareness of criminal aliens in the United States, the Secretary (of DHS) and the Attorney General are hereby directed to collect relevant data and provide quarterly reports on the following: (a) the immigration status of all aliens incarcerated under the supervision of the Federal Bureau of Prisons; (b) the immigration status of all aliens incarcerated as federal pretrial detainees under the supervision of the United States Marshals Service; and (c) the immigration status of all convicted aliens incarcerated in state prisons and local detention centers throughout the United States."

The new statistics could give researchers, and the general public, a much better idea of the extent of crimes involving suspects in the country illegally.

Trump's orders stop short of measures that would require the approval of Congress, such as resetting the numbers of immigrants allowed to enter the country each year. But they still go a long way. And the early response among Republicans on Capitol Hill was encouraging for the new administration.

Trump will undoubtedly have proposals for Congress on immigration. But his two executive orders go a long way toward undoing the practices that Barack Obama unilaterally set in place. If Trump makes sure his orders are enforced, he will have kept a major promise to those who elected him.